This invention relates generally to steering columns for motor vehicles and, more particularly, to steering columns that have a steering shaft supported by a bearing within a housing.
Current automotive steering columns require bearings that provide high stiffness without high torque, even when operating with misalignment and variations in press fit of the bearing. A preferred type of bearing for such applications is a zero clearance ball bearing. Generally, the bearings that are used have a full complement of balls because there is inadequate space for a cage or ball separator. However, when the bearings are under load, the balls contact each other and bind, causing high torque spikes. This condition is known as xe2x80x9cball gaggingxe2x80x9d.
The trend is for automotive manufacturers to increase steering column natural frequency, requiring higher and higher bearing stiffness. Current bearing designs can only marginally meet today""s requirements, even with 100 percent inspection by hand and a significant percentage of bearings being rejected as scrap. Further increases in bearing preload, as a means to increase bearing stiffness beyond today""s levels, are not possible with the current bearing designs because of the high torque spikes caused by ball gagging.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the invention, this is accomplished by providing a housed steering column comprising a steering shaft, a housing enclosing at least a portion of the steering shaft, and a preloaded ball bearing mounted within the housing and supporting the steering shaft. The preloaded ball bearing has loaded balls that are preloaded and unloaded balls that are free floating, an unloaded ball being positioned between each loaded ball. A split raceway provides two angular contact raceways that are preloaded axially against the loaded balls.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.